西藏狮泉河地区仁温斜长花岗岩LA-ICP-MS锆石U-Pb年龄及其构造意义  

LA-ICP-MS zircon U-Pb age of Renwen plagiogranite pluton in Shiquan River area, Tibet

作　　者：尼玛次仁[1,2] 王国灿[2] 顿都 叶强 普尺 焦文龙 次仁央宗 洛桑朗杰 李开云 

机构地区：[1]西藏地勘局区域地质调查大队,西藏堆龙德庆851400 [2]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地质通报》2015年第12期2246-2253,共8页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212011121232;1212011221057)

摘　　要：西藏狮泉河地区仁温斜长花岗岩主要由更长石、石英等组成,Si O2含量为72.05%～72.83%,Al2O3含量12.72%～13.54%（〈15%）,Mg O含量1.19%～1.24%,Mg#值35.73～42.27（〈50）,Na2O含量介于4.56%～4.74%之间,K2O含量较低,在0.34%～0.57%之间,Na2O/K2O值为8.32～13.41,属低钾钙碱性系列岩石。斜长花岗岩与变质基性岩的地球化学特征表明,仁温斜长花岗岩可能是变质基性岩部分熔融形成的,该岩石中Sr、Rb、Ba等大离子亲石元素富集,Nb、Ta、Ti等高场强元素明显亏损,具有岛弧型火山岩的特征。用LA-ICP-MS法测得斜长花岗岩锆石U-Pb年龄为162.5±2.6Ma,表明狮泉河结合带（北亚带）在中侏罗世已发生俯冲作用。The Renwen plagiogranite in Shiquan River area of Tibet consists of oligoclase, quartz, etc. The zircon U-Pb weighted average age measured by LA-ICP-MS is 162.5±2.6Ma. The major elements are characterized by Si O2 content from 72.05% to72.83%, Al2O3 content from 12.72% to 13.54%, Mg O content from 1.19% to 1.24%, Mg#values from 35.73 to 42.27, Na2 O content from 4.56% to 4.74%, low K2 O content from 0.34% to 0.57%, and Na2O/K2 O values from 8.32 to 13.41. The major element geochemistry of Renwen plagiogranite belongs to low potassium calc-alkaline series. Geochemical characteristics of plagiogranite and metabasite suggest that the Renwen plagiogranite may have been derived from partial melting of metabasite, which shows island-arc volcanic characteristics, being enriched in LILE such as Rb, Sr, Ba and depleted in HFSE such as Nb, Ta, Ti. It is concluded that subduction took place in Middle Jurassic in the Shiquanhe suture（the north branch）.

关 键 词：狮泉河地区 斜长花岗岩 LA-ICP-MS锆石U-PB年龄 中侏罗世 

分 类 号：P534.51[天文地球—古生物学与地层学] P597.3[天文地球—地质学]